Fuel delivery systems for use with internal combustion engines are available in many different varieties, with two of the more common being the port fuel injection (PFI) system and the spark-ignited direct injection (SIDI) system. A PFI system utilizes a series or bank of fuel injectors each delivering a calibrated amount of fuel to an inlet port of an associated combustion chamber in the engine. In a SIDI system, a fuel injector is provided within each cylinder head of the engine. The injector injects a predetermined amount of fuel directly into the combustion chamber rather than to the inlet port. Fuel pressures within the combustion chamber can be orders of magnitude greater than the pressures which are present at the inlet port, and therefore certain components of a SIDI system operate at a higher relative fuel pressure than do the similar components of a PFI system. As a result, a SIDI system-equipped engine can provide a higher peak power level than can a PFI system-equipped engine, and thus improved relative fuel economy and emissions levels, due in large part to the precise metering of the fuel and an improved intake of air into the combustion chamber of the SIDI engine.
When an internal combustion engine is idling, fuel continues to be consumed by the engine for the purpose of running or powering the various vehicle systems and accessories. In a PFI engine mated with a conventional automatic transmission, engine flare control during a transition to a run state from an idle state during cranking can be less than optimal due in part to air loop dynamics and homogeneous fuel combustion constraints. Also, while the higher initial fuel pressures provided by a SIDI engine, or other direct-start engine styles such as a diesel engine, provide certain efficiency gains relative to the PFI engine, neither engine design is optimally constructed for maintaining automatic transmission functionality when the engine is off, or during rapid cranking and starting of the engine from an idling state.